Posted
by
timothy
on Wednesday November 05, 2003 @03:51PM
from the send-more-satellites dept.

letxa2000 writes "CNN is reporting that Voyager 1, now some 8.4 billion miles (90 AUs) from the sun, has left the solar system and entered interstellar space by reaching the heliopause. However, whether the probe has reached the heliopause or is just coming close is the subject of two papers to be published in Thursday's Nature Magazine. The probe supposedly has enough nuclear fuel to last until 2020. Will it be able to find anything interesting outside the solar system in the next 17 years?"

Not much really. Neither the probe nor the space it "travels through" actually required any simulation at all. We only needed to simulate the probe's signal back to earth, and the data it "generated", which was merely made up from preconceived expecations, anyway. The humans were happy, and all is right with the world.

Will it be able to find anything interesting outside the solar system
in the next 17 years?

Short answer: No.

Long Answer: "Space is big. Really big. You just won't believe how vastly
hugely mind-bogglingly big it is. I mean, you may think it's a long way down
the road to the chemist, but that's just peanuts to space... " -DNA

Questions that can still be investigated by Voyager include a number of questions about the interaction between the solar wind, solar magnetic field, and interstellar medium, direct measurements of the interstellar magnetic field, the actual composition of interstellar gas, where exactly the heliopause lies, and how it's affected by changes in solar activity. I'm sure there are even more questions that I haven't thought of.

2. Getting useful information about space from telemetry means you have to track an object which you know the properties of. We know approximate mass for most comets. We know exact mass, composition, initial velocity, acceleration vectors and more about Voyager. This means we don't have to guess these in calculations, which means we get quite a bit more detailed info out of them.

According to Wikipedia, you're right; Oort Clouds are postulated to extend 50,000-100,000 AU from their stars.

That would effectively put Voyager outside the heliopause but still within Sol's Oort cloud.

I like the end of the Wikipedia article:

It is thought that other stars are likely to possess Oort clouds of their own, and that the outer edges of two nearby stars' Oort clouds may sometimes overlap, causing the occasional intrusion of a comet into the inner solar system.

Voyager has been moving through space in ways unexplainable by physics. There is a small acceleration that can't be accounted for using known laws. It's almost like gravity doesn't work quite the way we think it does.

Of course, there is always the possibility that we just can't see the source of the acceleration, and it'll turn out to be something simple. However so far, all proposals put forth to explain it have been shown to be incorrect.

There is a deeper connection to very important issues in physics. For decades we have been studying the fabled "dark matter" which is supposed to be the cause of the anomalous rotation of the galaxy. The galaxy does not move in ways predicted by the laws of gravity. It is as if there is a huge amount of hidden mass which is influencing its rotation. So far we have not found any of this "dark matter."

But imagine the possibility. What if dark matter doesn't really exist? What if it's our understanding of gravity that is wrong? This would have profound implications throughout physics. After all our only direct experience of gravity is what happens here on Earth and within the bounds of the solar system. Except that today, we have a probe that has crossed that limit.

Perhaps the anomalous motion of Voyager will shed light on the situation. I for one would be utterly elated if it turns out we have to rewrite our physics books.

Actually it's pretty well understood that our theory of gravity is wrong. It doesn't agree with quantum mechanics. That's the big push in physics right now to find a 'quantum' theory of gravity, or identify the graviton particle.

Well, there's a difference between being correct and being accurate. Yes, clearly our current theory of gravity is not CORRECT because it doesn't play well with QM. However it is a very ACCURATE theory in the sense that it gives answers which match reality exceedingly well (unless you take things to the quantum scale).

What we're talking about here is a new situation, where the current theories of gravity aren't giving the right numbers even at a macroscopic scale. That is, if there isn't some other hidden

Voyager has been moving through space in ways unexplainable by physics.

Any references I can read? astro-ph will do fine...:-)

So far we have not found any of this "dark matter."

Oh yes, there are many detections of massive astrophysical compact halo objects in our galaxy, P. Popowski et al [arxiv.org], and there is also a lot of work going on to use the same ideas to look for similar bodies in other galaxies. In fact, the microlensing ideas were first proposed for extragalactic studies by Chang and Refsdal i

The spacecraft in question wasn't Voyager, but PIONEER 10. My point stands however, that having probes in the far reaches of space away from the solar system will be extremely valuable in the study of theories of gravity. Here's a link to a good place [buckyballmusic.com] to start. A good Google search is "pioneer anomalous acceleration"

Near the end of the article I linked, they explain that this effect is not observed with Voyager because of the way Voyager is stabilized by boosters (as opposed to spin-stabilization for Pioneer). If the effect is occurring with Voyager it is completely swamped by the booster accelerations. They also indicate that (obviously) the best way to continue studying this is to launch another probe outside of the solar system.

If you spend any time researching this, you'll find groups of people all over the place who claim to have explained it. But none of them agree with each other. I think it's accurate to say that nobody REALLY knows what's happening.

I only have one problem with the whole dyson sphere idea. Assuming you are trying to walk around inside it, what is going to keep you on the ground? Not gravity.
One of the problems we had to deal with in my college physics courses was figuring out the effect of gravity on an object inside a shell, resultant from that shell. And you know the answer we came up with? Zero, Zilch, the gravity from the shell counteracts itself no matter where you are in the shell. Simply put, even though you are might be c

from-JPL.NASA [nasa.gov]
"The solar system does not end at the orbit of Pluto, the ninth planet. Nor does it end at the heliopause boundary, where the solar wind can no longer continue to expand outward against the interstellar wind. It extends over a thousand times farther out where a swarm of small cometary nuclei, termed Oort's Cloud, is barely held in orbit by the Sun's gravity, feeble at such a great distance. Voyager 1 passed above the orbit of Pluto in May 1988, and Voyager 2 will pass beneath Pluto's orbit i

actually, kinda... it's the sound of a deep bass, which the human ear can't hear... they found out because they noticed it shifted planets and stars along it's wave... check it out here: space.com [space.com]

The heliopause is the boundary where our Sun's solar wind is stopped by the interstellar medium.

The solar wind blows a "bubble" in the interstellar medium (the rareified hydrogen and helium gas that permeates the galaxy). The point where the solar wind's strength is no longer great enough to push back the interstellar medium is known as the heliopause, and is often considered to be the outer "border" of the solar system.

The distance to the heliopause is not precisely known. It is probably much smaller on the side of the solar system facing the orbital motion through the galaxy. It may also vary depending on the current velocity of the solar wind and the local density of the interstellar medium. It is known to lie far outside the orbit of Pluto. The current mission of the Voyager 1 and 2 spacecraft is to find and study the heliopause.

An alternative definition is that the heliopause is the magnetopause between the solar system's magnetosphere and the galaxy's plasma currents.

What's the range of communications for the probe? When will we lose our connection (if we haven't already)?

No one knows for certain. A number of factors enter in, including the ability of Voyager to keep its antenna pointed at Earth, the amount of power left in the radiothermal generator, the size of radio telescope available for communicating with it on Earth, and possibly unknown effects from the heliopause.

What's the range of communications for the probe? When will we lose our connection (if we haven't already)?

For many years I was a co-investigator on Voyager (actually, technically, I suppose that I still am; I have never been notified that the status ever changed). Anyway, the best guess when I was an active participant, throughout the 80s and half of the 90s, was more-or-less the year 2010. That was predicted to be the year at which the always-decreasing power output from the transmitter, the ever-increasing distance and the more-or-less constant sensitivity of the DSN (Deep Space Network) system combined to reduce the received signal to the point where it the bit rate at which information could be extracted was too low to be useful.

The general supposition was that funding would be eliminated before that date.

I suppose if they felt they were still getting useful information from the probe (ie, it was "looking" at something "interesting" with sensors that still worked), they could always launch a relay-type satellite... just like a network repeater.

Good thing they have several years to decide both if they:
A) want to have/fund such a thing
B) are getting new information worth collecting

Heck... who knows where our terrestrial (or even space-stationed) receiver technology will be in 5 years; perhaps we'll be able to pick out the signal from here, no matter how weak nor how noisy.

you cant launch a relay satellite. Remember, the falloff is r^2. Even the best engines would take about 10 years to place a satellite halfway between voyager and earth.that would be 2015 or so. Now the energy density at the point of the satellite would be 4 times as high as on earth, BUT there is no way you can stuff a reviever on a satellite who as 5% of the sensitivity of a earth based reciever. Remember, on earth you could use 300m at arichbo. For 4 times the signal power, you would still need a 150m dis

First of all, the primary issue with the signal falloff is the SIZE of the reciever. Launching a sattellite doesn't exactly solve that problem, because the sattelite's reciever would have to be *nearly* as large as the VLA or the big "lake sized" earth-bound dishes.

I think it has more to do with the sheer size, than the sensitivity of the reciever. The "noise" from the Universe will eventually eat the signal and with the combination of decreasing power and increasing distance, I think xmit power will fall off faster than some "technology" (new filters, transforms, etc etc)

What is this fuel used for? Just for communicating, or does it still need acceleration? If it's just for communication, couldn't they make it last longer by increasing the intervals between each time it communicates?

It's just used for sensors and communication, but it's a nuclear fuel, and it's goiong to decay whether we use the energy or not. Plutonium's half-life is Plutonium's half-life, and there's not anything we can do about that...

I should hope its doing more than just communicating its existence to us. While it may not need to accelerate (it may, I don't know), it does have various instruments on it for measurements and observations, so that it has something to communicate to us beyond a simple "Hello."-N

It's only got a few things it needs to do: keep the antenna pointed (roughly) at Earth, run the few instruments still active (the camera, for example, has been turned off), and occasionally communicate.

Voyager uses a radioisotope thermoelectric generator for its power. This means that radioactive decay of its fuel creates heat, which is used to create power. That fuel's going to decay no matter what, so you either use the power or lose it.

What is this fuel used for? Just for communicating, or does it still need acceleration? If it's just for communication, couldn't they make it last longer by increasing the intervals between each time it communicates?

I believe they are talking about the nuclear battery that's onboard to power it's 20watt transmitter. Near as I remember the decay of plutonium causes heat which keeps the craft warm and operational, and is used to generate power. Given that this was launched in 1978, this is a major acco

Don't forget the Yankee Stadium analogy: The sun is on home plate, the first 4 planets are between home and the pitcher's mound, Jupiter is on second base, Saturn and Uranus are in the outfield, Pluto is in the parking lot, and Centauri is in San Franciso.

of how scientists do not take the next big leap. What frightens me the most is that we have not sent more probes after Voyager.

Coming up is a planetary alignment that would allow a route to Tau Ceti, one of the reasonably nearby stars that could have an inhabitable planet. Using modern high-velocity nuclear engines, a probe could be engineered to reach it in 100 years, roughly. And a craft could be engineered to actually survive the travel *and* send back useful data.

I want to see interstellar probes, engineered to travel to the nearest (12ly or less) stars and explore them.

Funny thing about large timeframes and technology -- if you wait long enough you will actually be further ahead.

Exploring this solar system with experimental high-velocity nuclear engines is appropriate. But in 20 years we could probably send something to the nearest stars in 50 years. In 40 years perhaps it will only take 25 to travel -- thus we should wait 40 years before launching to arrive first:)

I wonder if we'll ever see space technology advance enough so that, one day, we might be able to send a spacecraft past Voyager. Maybe we'll have some form of near-light-speed travel, or even faster-than-light travel, and manage to reach other stellar systems before Voyager does ?

In any case, I'll be more than satisfied if we establish a colony on Mars, tag me a conservative if you will, but I don't feel like leaving good old Sol just yet.

The Voyager probes weren't built for speed. They were coasters, zipping from gravity well to gravity well with just a few puffs from the steering jets now and then.

If there were some pressing reason to catch up, we could do it, although it would be pricey due to the current high cost of getting things into orbit. You'd need to get something up there with a motor capable of adding substantial change in velocity. A big liquid fueled motor, or perhaps one of those new-fangled ion drives powered

Here's hoping that the only pre-requisite for other species to be allowed to engage in interstellar contact with yours is to build a probe that leaves your solar system. Gort shoudl be arriving anyday now to lay down the law.

Indeed, science can be distilled down to a set of little sound-bite facts that are easily repeatable. "There is no sound in space" is one of them. However what most people for some reason do not understand is that this is a SOUND BITE.

It is far too common for Slashdot readers to immediately object to something because it clashes with their boiled down kiddy version of science.

Here's some news for you: the space surrounding the sun is far from empty, in fact it is filled with atoms, electrons, and ionized gas. Its density is low enough that a human would not perceive it without an instrument. But sound can quite easily travel through gas, no matter how thin. Clearly the sound cannot travel any faster than the individual particles themselves are moving. Hence it is very easy to define the speed of sound in a gas.

No, I'm not claiming to be a scientist or above anyone else in terms of scientific knowledge, but it really pisses me off when people's first reaction is to DOUBT THE SCIENTISTS. Sure, they can be wrong sometimes, but I think it would be respectful to go do a little research before claiming, as if you are some kind of expert, that they are wrong.

In a sparse gas where interparticle interactions are uncommon (they don't hit each other frequently), the speed of sound depends only on temperature and not density.

(going from water to air is a speed increase, and I'm guessing its some function of density)

That's backward, sound travels much faster through water than through air. It does relate to density but not directly. The quantities that influence the speed of sound are the temperature and something called "bulk modulus" which describes how the material density changes as the pressure changes. Temperature is more important at very low densities. At higher densities as in solids the bulk modulus is the primary factor.

Voyager crash lands on this deep and remote planet..as each of its systems start to shutdown in turn, its external microphones pick up the voice of Charleston Heston, screaming in the distance "Take your paws off me you damn dirty ape!"....
[muffled horse hooves pounding on the ground]
Voyager 1 signing off. Goodbye earth...
;-)

Wow I should only hope to make a piece of code that lasts so long (the best I did is 3), a true testament to what a bunch of nerds with some ingenuity (and money) can really do. These days it seems we have the genius, but surely not the money. Oh well...

Sssh.. You missed your calling with the guys who wrote the software with the Y2K bug in it!

Yes... kinda feeling old (I just turned 36) but I remember when Voyager was launched. It was emotional then, and its emotional now. Think: back then, 640k was a *lot*, and the standard logic was 7xxx series TTL chips. Dunno what CPU, but I doubt it was anything so advanced as a Z-80. Dunno what firmware either, if any - coulda been hardwired. Can't remember shit here.

Now, if you ask me: That's a beautiful piece of engineering, that we're still getting some use from.

I worked at JPL for the power group, so I can actually say something about this. All of the deep-space probes run on radiothermal generators. What this is basically a radioactive source surrounded by thermoelectric generators and alpha particle absorbers. Thus, both the thermal gradient established between the radioactive material and space (via heat pipes and radiators) and the alpha particles emitted by the radioactive material are able to generate power.
There are two limitations on the lifetime of these generators - the lifetime of the radioactive isotope, and the durability of the thermoelectrics and alpha particle absorbers. I don't know too much about the particle absorbers, but I worked with the thermoelectrics, and there are durability runs of several years. However, Voyager is far older then any test we could ever do. My feeling in this is that barring high-heat conditions, the thermoelectrics should be able to last nearly indefinitely.

I'm not sure why I'm bothering to respond to this obvious troll, but here goes...

We already have enough resources to take care of all the needy people not only in this country but on this planet. The real problem is that society, as a whole, just doesn't care enough about the unfortunates enough to do anything. If we were to stop sending any money on space exploration, that money would not get immediately diverted to persons in need. It would most likely end up funding tax breaks so that people can buy a new SUV. Or maybe it would "disappear" in a S&L fraud or HUD "misappropriation".

I grow tired of hearing people complaining that we should divert money from science towards needed social programs. Those programs are underfunded because we just haven't made them a priority. Slashing someone else's budget isn't going to make that money magically appear in the budget of social programs. We would need a real fundamental change in attitudes of elected officials and the voting public.

Many, many homeless simply cannot be helped. The borderline mentally ill would have to be forced into homes - which would violate their rights under the constitution. Addicts would have to be forced into treatment, which again, barring the commission of a crime, would violate their rights.

If you were homeless, and wanted help, it's out there. Noones going to build you a 200,000 home and hand you the keys, but if you need a mailing address, a shower and shave, a ho

"The real problem is that society, as a whole, just doesn't care enough about the unfortunates enough to do anything."

Funny, when I read this, a memory bubbled to the surface. I was at a fast food joint one night. A homeless woman tapped my shoulder and asked for money to buy food. Thinking "hey, we're in a restaraunt, she'll actually use the money to buy food!" I gave her $5. She turned right around, wandered outside, and headed in the direction of a nearby shopping center complete with liquor store. The woman next to me in line was astonished. I wasn't terribly happy about that.

Can't entirely blame society here. The whole 'teach a man to fish he can eat for a life time' story comes to mind. It's hard to buy a homeless guy a meal and let him go off to bum a meal off of somebody else the next day. I can give him my money, but what will he do to help himself?

Society's not generally being cold hearted here. They are, however, closing themselves off from being taken advantage of. I don't have a solution to the homeless problem, but I'm reasonably confident that feeding them isn't the answer. They need to be made independent. Show me a way I can contribute to that, and I'm all ears.

Don't assume people don't care. They do care. The problem is the solution isn't there.

when his disciples were anointing his turban with expensive olive oil and they wondered why they shouldn't spend that money on the poor, instead of turban oil, "the poor will always be with us."

I'm sure if you met most of those hungry, homeless sorts, you'd find them to be mentally ill people who refuse to take their medidine. Now, 30 years ago, they could be forced to take their medicine, but since those touchy feely sorts got into power, they said it's against human rights to force them to take medicine.

No one need go to bed hungry in the U.S. - regardless of what we spend on space exploration. The food already exists and it is purely a matter of distribution. In fact I would say that anyone who goes to bed hungry tonight did not take advantage of services that already exist that could feed them.

Outside the U.S. it is a bit more complicated. But here- we throw out enough every day to feed a lot more than 2 million.

Give a man a fish - and he will eat dinner. Teach a man to fish and he can feed himself for life.

Why should we worry about feeding people that don't want to bother helping themselves. I am much more concerned with the percentage of the population (20% rather than the 1% that you report as going hungry) that is overeating and obese (not just fat - but obese)

Basic science has a payback much higher than the costs to do the research... it is a very good investment (if you don't think so - get off the intern

Why is it that we can brainwash the masses into thinking that it's okay for us to spend billions on space crap while ignoring the homeless people living in the streets and at the YMCA?

You are very shortsighted. Funding technology research creates new solutions to age-old problems. One day, a technology will be invented that makes hunger obselete (as in the Star Trek future). This technology is only limited by will, means, and time.

Simply giving the money to the poor solves nothing. So they can buy pi

Would "we the people" ever hear about it? Or would the find be a classified secret due to so-called national/international security risks and issues?

It wouldn't matter whether it was classified or not. A secret that big would not stay a secret for long. There are leaks all the time. Christ, we've already managed to let the Chinese obtain detailed information about every nuclear weapon in our arsenal. I'm sure if we ever got a clear sign of extraterrestial intelligence, word would slip out in a matter